Portland cement is one of the most important materials in the construction industry because of its multiple applications and chemical and physical properties. However, the costs and volume used are important factors that have lead to the search for new materials for replacing a part of the cement needed for such usage. The search for new materials has also led to a search for new materials that will lead to improved products.
General awareness in the 1980's of the deterioration of cement structures prompted many researchers to search for new materials which satisfy the strength criteria, but also the durability requirements. For example, researchers in the development of high performance cement (HPC) have made considerable progress. New constituents have been investigated and they are mostly from active silica (pozzolanic materials) that are obtained from natural deposits such as metakoalin or industrial waste such as fine silica fume, fly ash and ground blast furnace slag or agricultural waste such as rice husk ash.
In a sense, the pozzolanic materials have become very relevant due to their capacity to interact with the cement components and to improve its properties. The pozzolanics are siliceous or silica-aluminous materials that in themselves have little or no cementitious value, but in finely divided form and in the presence of moisture chemically react with calcium hydroxide at ordinary temperatures to generate compounds processing cementitious properties.
Pozzolanic materials such as silica fume and fly ash are considered to be basic materials for the production of HPC. However, as costs for these materials have increased and their availability threatens to pose problems for the sustainable production of certain concrete products. There is a need for less expensive materials for the partial replacement of cement in concrete products. It has also been recognized that civil construction applications such as roads, bridges, commercial and residential buildings, etc. that require significant amounts of cement based concrete would benefit from a lower cementitious material that reduces the demand for cement and dependency on the availability of pozzalonic materials.
Researchers have attempted to find cheaper and more readily available materials as partial replacements for cement. For example, a U.S. Pat. No. 5,820,668 of Comrie discloses an inorganic binder composition that may be used in partial substitution for Portland cement. The inorganic binder composition includes materials such as fly ash, Al2O3, pozzolan, ground slag, nephelene cyanite, anhydrous aluminum silicate, hydrous aluminum silicate, hydrous sodium hydroxide, silicic acid, potassium salt, and sodium salt.
A more recent Published Patent Application No. 2005/016096 of Comrie also discloses cementitious materials including stainless steel slag and geopolymer that can be added to conventional cement compositions, such as Portland cement as a partial or total replacement for conventional cement materials. The stainless steel slag may comprise silicates and/or oxides of calcium, silicon, magnesium, iron, aluminum, manganese, titanium, sulfur, chromium and/or nickel. The geopolymer may comprise aluminum silicate and/or magnesium silicate. In a preferred embodiment, curing of concrete materials by the action of water on the cementitious materials is enhanced with the addition of an activator component selected from calcium bromide, calcium nitrate, calcium nitrite, calcium chloride, calcium oxide, and sodium bromide.
Notwithstanding the above, it is presently believed that there is a need for and a potential commercial market for a cement/aggregate composition, concrete product and method for making a concrete product in accordance with the present invention. There should be a demand because such products blend up to 30% of the cement with a relatively low cost, naturally occurring material that is readily available in a relatively large amount.